Effects of sand-mulch thickness on soil evaporation during the freeze–thaw period

Control of evaporation from seasonally frozen soil is an important method for alleviating water shortages in arid and semi-arid areas. To investigate the inhibition of soil evaporation by sand and the major factors that influence soil evaporation, a series of field experiments with five sand-mulch thicknesses (0 cm, bare soil [BS], 1 cm [T1], 2 cm [T2], 3 cm [T3] and 4 cm [T4], with an average diameter of 1 mm) were conducted during the freeze–thaw period in Northern China. Soil evaporation characteristics in the three freeze–thaw stages were revealed and the major factors influencing soil evaporation were analysed using grey correlation analysis. The results showed that the cumulative soil evaporation decreased with increasing sand-mulch thickness during the freeze–thaw period, and only small differences in soil evaporation were observed between the T3 and T4 treatments. The reduction in soil evaporation under different sand-mulch thicknesses was 19.2–62.6% in the unstable freezing stage (P1), 2.0–28.3% in the stable freezing stage (P2) and 4.8–20.4% in the thawing stage (P3). In P1, solar radiation was a major factor influencing soil evaporation in all treatments and vapour pressure was a major factor in the sand-mulch treatments, and the influence of relative humidity on soil evaporation decreased in the T4 treatment. During the coldest P2, solar radiation was lowest so that relative humidity and wind speed became the more dominant influence factors on soil evaporation in all treatments, and surface soil water content was a major factor in the sand-mulch treatments. In P3, average air temperature and solar radiation were major factor influencing soil evaporation in all treatments and vapour pressure was a major factor in the BS and T1 treatments, whereas water surface evaporation was the major factor in the T2, T3 and T4 treatments. The results suggest that the addition of sand mulch in agricultural fields may be a beneficial practice to reduce water stress in arid and semi-arid areas.     

Structure of the latitudinal profile of solar cosmic rays in the Earth’s magnetosphere during substorm activity on October 26–27, 2003

The structure of penetration of solar cosmic rays (SCRs) with energies of 1–100 MeV into the Earth’s magnetosphere before a strong magnetic storm of October 29–31, 2003, is studied based on the CORONAS-F satellite data. The effect of north-south asymmetry was observed in the polar caps for more than 12 h, which made it possible to study the dynamics of the boundary between the polar cap (the magnetotail) and the auroral zone (the quasi-trapping region). A previously unknown effect of dropouts in the SCR intensity latitudinal profile during the substorm active phases has been detected in the auroral magnetosphere. The mechanism by which dropouts are formed owing to the local distortion of the magnetic field line configuration, resulting in radial diffusion of particles from this region, has been proposed.     

Transverse resonance in the high-latitude section of the Earth–ionosphere waveguide during the solar eclipse of March 20, 2015

The spectra of radio atmospheric signals (spherics) recorded simultaneously at two observatories of the Polar Geophysical Institute, Lovozero (67.97° N, 35.08° E) and Barentsburg (78.08° N, 14.22° E), during the solar eclipse on March 20, 2015 are presented. The peculiarities of the behavior of the first critical frequency of the Earth-ionosphere waveguide during the eclipse are described. The effective altitude of the reflective layer of ionosphere is assessed.     

Characteristics of Pc4–5 pulsations obtained using the method of bistatic backscatter of HF radio waves,the EISCAT HF heating facility,and ground-based magnetometers

The results of studying the Pc4–5 pulsation parameters based on the method of bistatic backscatter of radio waves, using the EISCAT/Heating HF facility (Tromsø, Norway) and IMAGE ground-based magnetometers (Scandinavia), are presented. The observations were performed during the morning hours on October 3, 2006, when a substorm developed on the nightside. An analysis of the observational data obtained from 1000 to 1020 UT indicated that wave-like disturbances with periods corresponding to Pc4–5 pulsations (80–240 s) existed at that time. The variations in the full vector of the ionospheric irregularity motion and the electric field strength in an artificially disturbed high-latitude ionospheric F region has been reconstructed based on simultaneous Doppler observations on two paths. A general conformity is observed among the time variations in Pc4–5 pulsations in the magnetic and ionospheric data: between the velocity amplitude (|V|) and the X component of the Earth’s magnetic field and between the irregularity motion azimuth and the Y component. Large-scale waves, corresponding to the natural resonances of magnetic field lines (small values of the azimuthal number |m| ～ 2–4), and small-scale waves (large values |m| ～ 17–20) were simultaneously registered during the experiment based on magnetic data. It has been indicated that the periods of wave-like processes registered using the method of bistatic backscatter and ground-based magnetometers were in agreement with one another. The formation of wave-like processes is explained by the nonstationary impact of the solar wind and IMF on the Earth’s magnetosphere. The variations in the IMF, according to the ACE satellite measurements, were characterized by a sharp increase in the solar wind plasma dynamic pressure that occurred at about 09 UT on October 3, 2006, and was accompanied by rapid polarity reversals of the north-ward-southward (B _z) and transverse (B _y) IMF components.     

The temporal evolution of the large equatorial plasma depletions observed during the 29–30 October 2003 storm

This study investigates the temporal evolution of the large plasma depletions observed by ROCSAT-1 and DMSP near 295°E during the 29–30 October 2003 storm. The presence of a penetration electric field around the detection time of the large plasma depletions is supported by the observation of high upward ion drift velocity and formation of an intense equatorial ionization anomaly in the American sector. However, these ionospheric disturbances occur in broad longitude regions; a short-range polarization electric field may adequately explain the creation of the large plasma depletions. The penetration electric field may trigger the Rayleigh–Taylor instability and produce abnormally large plasma depletions during the storm. The TIMED/GUVI and CHAMP observations provide an insight for the evolution of the large depletions several hours after their formation. The large depletions appear as arch-shaped emission depletions in the TIMED/GUVI image and as symmetric depletions paired in the magnetic north and south in the CHAMP observation. These characteristics can be explained by the “plasma depletion shell” phenomenon (Kil et al., 2009) produced by the westward shear flow of the ionosphere during the storm.     

Changes in the height of the active Karymskii Volcano, Kamchatka during the period 1971–2007

Systematic measurements of the height of the summit crater rim on the active Karymskii Volcano showed that the variation of that parameter has been greater during its last eruption, lasting, with short intermissions, from January 1, 1996 until now (October 2007) compared with the earlier eruptions. The periodic increases in the height of Karymskii Volcano were due to explosion discharges of unconsolidated pyroclastic material, with most of this falling on the volcano’s cone. The increased seismicity of Karymskii Volcano intensified the slope movement processes, resulting in a comparatively flat area forming periodically on the crater rim; during separate, not very long, periods the height of the volcanic cone was increasing in discrete steps and at a greater rate. The periodic decrease in the height of Karymskii Volcano is due to compaction of pyroclastic material and, to a much greater extent, after violent explosions which expand the crater by removing its nearsummit circumference. The other contributing factor consists in sagging of the magma column due to partial emptying of the peripheral magma chamber, which makes the internal crater slope steeper, hence causes cone collapse and the cone lower. These occurrences are generally similar to the processes of crater and caldera generation described by previous investigators for other volcanoes of the world.     

High-latitude ionosphere during magnetic storms of October 26, 2003–November 1, 2003: Tomographic reconstructions and numerical modeling

The height-latitude distributions of the electron density in the European Arctic sector of the subauroral and high-latitude ionosphere have been reconstructed based on the data of satellite radio tomography. The reconstructions have been compared with the results of the numerical modeling obtained using the UAM global numerical model and the IRI-2001 empirical ionospheric model. The goal of the paper was to find the degree of adequacy of these models to the observational data during geomagnetic disturbances. The UAM theoretical model adequately reproduces the dynamics of the main ionospheric trough, in particular, the position of its equatorward wall, and to a certain degree better describes the behavior of the high-latitude ion-osphere than the IRI empirical model. The discrepancies are observed in the regions of increased electron density poleward of the trough. To eliminate such disagreements, it was proposed to correct the model input distributions of precipitating high-energy electron fluxes with an energy of about 0.5 keV; i.e., the inverse problem of determining these distributions has been solved for extremely strong geomagnetic disturbances.     

Assessing the volumes of material discharged by Bezymyannyi Volcano during the 1955–2009 period

We present data on the volumes of material discharged during the main phases of the volcano’s recent activity from its start in October 1955 until December 2009. The amount of ash discharged onto the ground surface during the preculmination period (October 1955 to March 1956) is estimated as 400 million tons; the paroxysmal eruption of March 30, 1956 discharged more than 400 million tons, the volume of pyroclastic flows was estimated as 1416 million tons. The following estimates were obtained for the material discharged onto the ground surface for the period from 1956 to 2009. The weight of the lava cone that grew in the newly formed crater is 941 million tons, the deposits of pyroclastic flows weighed 491 million tons, and the ash weight was 117 million tons. Effusive activity was insignificant; the weight of the lava flows was ∼9.2 million tons. The amount of material erupted during the third phase is estimated as 1560 million tons. The mean annual discharge between April 1956 and December 2009 was 29 million tons. This figure is half that for the giant Klyuchevskoi volcano and six times larger than the mean discharge found for the 5000–5500 years of the existence of Bezymyannyi Volcano.     

Observations of mount etna seismicity during the 2002–2003 eruption based on deep-sea gravimeter data

This paper concerns observations made by a broadband deep-sea gravimeter installed on the plat-form of the SN-1 multiparameter seafloor observatory. The observatory was deployed at a distance of 25 km from the east coast of Sicily in southern Italy at a depth of 2105 m and was operated in a self-contained mode from October 2002 to February 2003 (134 days). The proximity to Mount Etna and the period of eruptive activity starting in late October 2002 lent added interest to this experiment. The seismic activity of Mount Etna, as recorded by the gravimeter, is characterized by the presence of two signal types, viz., a long-period volcanic tremor of variable amplitude and volcano-tectonic earthquakes. The bulk of energy in the long-period tremor occurs in the spectral interval between 2 and 5 s. The long-period seismic signals due to volcanic and global earthquakes were used to estimate resonant characteristics for Etna’s heterogeneous structures.     

Study on the Genesis of the Yongsheng Earthquake with Ms6.0 on October 27, 2001

On October 27, 2001, a large earthquake with Ms6.0, named the Yongsheng earthquake, occurred along the Jinshajiang segment of Chenghai fault in Yongsheng County, Yuunan Province. It is the largest event to occur along the Chenghai fault in the last 200 years. The seismo-geological survey shows that the seismogenic fault, which is the Jinshajiang segment of Chenghal fault, takes left-lateral strike-slip as its dominant movement pattern. According to differences in vertical motion, motion time, landforms and scales, the Chenhai fault can be divided into eight segments. The Jinshajiang segment has a vertical dislocation rate of 0.4mm/a, far lower than the mean rate of the Chenghai fault, about 2.0 mm/a. It‘ s deduced that the two sides of Jinshajiang segment “stuck“ tightly and hindered the strike-slip of the Chenghai fault. The strong earthquake distribution before this event shows that the Jinshajiang segment was in the seismic gap. The Chenghai fault, as a boundary of tectonic sub-blocks, makes the Northwest Yunnan block and the Middle Yunnan block move clockwise, and their margins move oppositely along the Chenghai fault. In the motion process of the Chenghai fault, structural hindrance and the seismic gap of strong earthquakes are propitious to the concentration and accumulation of structure stress. As a result, the Yongsheng Ms6.0 earthquake occurred. The Sujiazhuang-Shangangfu segment is similar to the Jinshajiang segment with a low vertical motion rate of 0.3 mm/a and in the seismic gap. So it‘s postulated that the segment may become a new structure hindrance, and the Yongsheng Ms6.0 earthquake may trigger the occurrence of future large earthquakes along this segment.     

Regimes of magma recharge and their control on the eruptive behaviour during the period 2001–2005 at Mt. Etna volcano

Mount Etna volcano (Italy) during the period 2001–2005 has undergone a period of intense eruptive activity marked by three large eruptions (2001, 2002–2003 and 2004–2005). These eruptions encompassed diverse eruptive styles and regimes: from intensely explosive, during 2001 and 2002–2003 eruptions, to exclusively effusive in the 2004–2005 event. In this work, we put forward the idea that these three eruptions are the response of the progressive arrival into the uppermost segment of the open-conduit system of a new magma, which was geochemically distinct in terms of trace element and Sr–Nd–Pb isotope signature from the products previously emitted by the Etnean volcano. The magma migrated upwards mainly through a peripheral tectonic system, which can be considered as eccentric in spite of its relative proximity to the main system. The ingress of the new magma and its gradual displacement from the eccentric system into the uppermost sector of the open-conduit gave rise to different eruptive behaviours. At the beginning, the ascent of the undegassed magma, able to exsolve a gas phase at depth, and its interaction with closed-system magma reservoirs less than 10 km deep gave rise to the explosive events of 2001 and 2002–2003. Later, when the same magma entered into the open-conduit system, it took part in the steady-state degassing and partially lost its volatile load, leading to a totally effusive eruption during the 2004–2005 event. One further consideration highlighted here is that in 2001–2005, migration of the feeding axis from an eccentric and peripheral position towards the main open-conduit has led to the development of a new vent (South East Crater 2) located at the eastern base of the South East Crater through which most of the subsequent Etnean activity occurred.     

Study on the Triggering Effect of the October, 2005 Pakistan Mw7.6 Earthquake on Its Aftershocks

The influences upon aftershocks of Coulomb failure stress change (CFSC) generated by the main-shock of the October 8, 2005, Pakistan earthquake are calculated and analyzed. The following factors are included in the calculation: (1) the difference between the pore fluid pressure and the medium elastic constant in the fault plane area and those of its surrounding medium; (2) the tectonic stress direction of the seismic source area; (3) the aftershock failure mechanism of aftershocks is calculated by stacking the tectonic stress with the stress change generated by the main-shock. Our study, which includes many factors, fits fairly well with the aftershock distribution. It indicates that most of the aftershocks were triggered by the Pakistan main-shock that occurred on October 8, 2005.     

Combined electromagnetic, geochemical and thermal surveys of Taal volcano (Philippines) during the period 2005–2006

Since 1572, 33 phreatic to phreatomagmatic eruptions have occurred on Taal volcano (Philippines), some of them causing several hundred casualties. Considering the time delay between two consecutive eruptions, there is an 88% probability that Taal volcano should have already erupted. Since 1992, several phases of seismic activity have been recorded accompanied by ground deformation, opening of fissures, and surface activity. The volcanic activity of Taal appears to be controlled by dike injections and magma supply, buffered by a hydrothermal system that releases fluids and heat through boiling and subsequent steaming. In early 2005, a multidisciplinary project was launched for studying the hydrothermal activity. To map the hydrothermal system, combined surveys were carried out to investigate self-potential, total magnetic field, ground temperature and carbon dioxide soil degassing, along with satellite thermal imaging of the Main Crater Lake. The elevated temperatures and high concentrations of carbon dioxide, as well as electromagnetic anomalies, indicate large-scale hydrothermal degassing. This process is enhanced along the tectonic features (e.g., crater rim and faults) of the volcano, while active fissures opened along the E–W northern flank during the 1992–1994 seismic activity. Heat and fluids from the hydrothermal system are essentially released in the northern part of the crater, which is bounded to the South by a suspected NW–SE fault along which seismicity seems to take place, and dikes are thought to be intruded. During the January 2005 surveys, a new seismic crisis started, and the felt earthquakes prompted spontaneous evacuation of hundreds of inhabitants living on the volcano. Repeated surveys show changes of self-potential, total magnetic field, and ground temperature with time, without any noticeable spatial enlargement. These observations suggest that the northern flank located between the crater rim and the 1992–1994 fissures is connected with a deep thermal source in Main crater and is reactivated during seismic crises. This sector could be subjected to flank failure.     

Definition of the core zone of the “westerlies-dominated climatic regime”, and its controlling factors during the instrumental period

The term "westerlies-dominated climatic regime" describes the pattern of precipitation/moisture variations between westerliesdominated arid Central Asia(ACA) and mid-latitude monsoon-dominated Asia on decadal to multi-millennial time scales. However, no attempts have been made to define its core region and the possible physical mechanisms responsible during the period of instrumental observations. The present study investigates the spatiotemporal variations of summer and winter precipitation on interannual to decadal time scales over mid-latitudes of the Eurasian continent using Empirical Orthogonal Function(EOF) analysis. Our results suggest the existence of an opposing pattern of summer precipitation variations between ACA and mid-latitude monsoon-dominated Asia and Mediterranean on decadal time scales. Based on these results, the core region influenced by the westerlies is outlined, including arid central Asia and Xinjiang in China(36°–54°N, 50°–90°E). By using monthly NCEP-NCAR reanalysis, the relationship between the "westerlies-dominated climatic regime" and atmospheric circulation were also analyzed. The combination of the zonal climatic teleconnection pattern and anomalous Indian Summer Monsoon Precipitation(ISMP) causes the precipitation characteristics of the "westerlies-dominated climatic regime" precipitation pattern. In addition, the Atlantic Multidecadal Oscillation(AMO) may also have an important effect on the "westerlies-dominated climatic regime".     

Geophysical effects of the interplanetary magnetic cloud on October 18–19, 1995, as deduced from observations at Irkutsk

During an interaction of the Earth’s magnetosphere with the interplanetary magnetic cloud on October 18–19, 1995, a great magnetic storm took place. Extremely intense disturbances of the geomagnetic field and ionosphere were recorded at the midlatitude observatory at Irkutsk (Φ′≈45°, Λ′≈177°, L≈2) in the course of the storm. The most important storm features in the ionosphere and magnetic field are: a significant decrease in the geomagnetic field Z component during the storm main phase; unusually large amplitudes of geomagnetic pulsations in the Pi1 frequency band; extremely low values of critical frequencies of the ionospheric F2-layer; an appearance of intense E_s-layers similar to auroral sporadic layers at the end of the recovery phase. These magnetic storm manifestations are typical for auroral and subauroral latitudes but are extremely rare in middle latitudes. We analyze the storm-time midlatitude phenomena and attempt to explore the magnetospheric storm processes using the data of ground observations of geomagnetic pulsations. It is concluded that the dominant mechanism responsible for the development of the October 18–19, 1995 storm is the quasi-stationary transport of plasma sheet particles up to L≈2 shells rather than multiple substorm injections of plasma clouds into the inner magnetosphere.